Tandem gas anchor



Jan. 1o, 1928.

H. N. MARSH TANDEM GAS ANCHOR Filed May 31'., 1927 I. Y f4 Patented Jan. 10, '1928, Y

N. MARSH., F LOS ANGELES, CALIFORNIA.

TANDEM Gas ANcHon.

Application illed Hay 81, 1927. Serial No. 185,550.

perhaps be dissolved in the oil under the high pressures existing in the oil sand or may possibly exist in the form of minute bubbles. If the former is actually the case, the gas will be and is liberated and separated from the oil in the form of bubbles when the pressure originally existing on the oil is reduced by the action of the pump by which it is lifted. The proportionof the gas thus separated from the oil may not be a large proportion of its weight, but it is usually a very large proportion of its volume. After the said release of pressure and in the deep wells now common, where the rock pressures are high and the gas content 5 is large, it is not at all unusualfor the gas to exceed by several times the volume of oil produced from the wells.

Some of this gas rises outside of thevpump into the casingy and makes its way harmo lessly to the casing head. A portion of the gas, however, separating in the form of bubbles,"s entrained by the oil and carried into the pump suction, and whatever gas so, passes into the pump barrel decreases by at j least this amount the quantity of the oil which the pump will lift. In consequence it is a common occurence to find that a 4pump will actually lift to the surface only a quarter of its actual displacement capacity, the balance of the pump capacity being consumed in uselessly pumping` gas. l

. The ordinary methods of constructing gas anchors are well known and a great many such devices are in common use. The general principle is to cause the bil to'ilow upward 'outside a partition by which 1t 1s kept from flowing directly .into the suction of the pump,

tition and nally upward into the pump suction itself. In passing the high point of this reverse How the gas bubbles are given ,an opportunity to rise through the oil in the casing and make their way to the surface without coming into the pump suctlon. i The velocity in the downpass, that is in the portion of the anchor device lying between the outer shieldv and the then downward inside such par.

ump suction proper, is sufficiently reduce to allow the entrained gas to rise faster than the oil Hows downward.

In wells of large diameter it is a simple matter to use a shield of sufficient diameter to permit very slow downward movement of the column of koil therein, allowing ample time for the gas bubbles to rise to the sur face and escape.A In the very deep wells now common, however, and which often exceed four thousand ,or even five thousand feet, the outer casing which lines the well proper is usually very small, often no larger than four and one-sixteenth inches inside diameter, and it has been found very diicult to get into this small casing a pump suction having suiicient area, a surrounding shield having enough greater diameter to produce an eiiiciently low rate of downward travel of the oil. and to leave room between this shield and the casing itself for the oil to pass upward over the top of the shield. Furthermore, the pump tubing used in deep wells is rarely larger than two and one-half inches pipe size. and it is considered bad practice to exceed this diameter in the construction of gas anchors for the reason that a gas anchor, if it overhangs the diameter of the tubing, is excessively liable to' be sanded in and to be left behind when the tubing and pump are withdrawn from the well. anchors in common use in deep wells are so vineiicien't as to be practically valueless.

I have discovered that by doubling the For these reasons most of the gas length of the gas anchor and by so dividing the suction tube that the device functions as two anchors, tandem in position but acting in multiple, the velocity of the oil at the highest point of its travel (at which it ceases to rise and enters on a downward course and at which point, if at all, it must disengage its content of gas) may be cut in two, and the effectiveness of the device for any given diameter be thus about doubled.

Other objects and advantages of my invention will appear from the following description 1n which reference is made to the attached drawings, which will be understood to be strictly diagrammatic, and in which Figure l represents my improved gas an-v chor partly in elevation and partly in cross section.

Figure 2 represents a cross section of Figure 1 on the line 2 2.

' working Figure 3 represents a cross sectionof Figure 1 Aon the line 3-3. v

Figure 4 is identical with Figure 1 ex cept that'fthe reference figures are omitted and arrows inserted to show the direction of flow of the oil-gas mixture, of the oil, and of the separated gas. Referring particularly to Figure 1, the lower end of the working barrel of the pump is represented at 1 and the lower end of the standing valve block at 4, these being of any ordinary or preferred construction and not being a part of my invention. 5 is a pump shoe threaded at its upper end at 29 to fit the lower end of the barrel and threaded internally at its lower end, as at 24, to receive a hollow block 6, which block is threaded externally, as at 24, to fit the coupling. 6 is threaded externally at 25 to fit the jacket 15, and is bored out and threaded internally, as at 26, to a diameter approximately equal to the internal diameter of the standing valve block, to receive the suction pipe 7.

The pipe 7 is preferably made of light material, as for instance 16 gauge seamless brass tubing, and the threads 26 should be the fine threads suitable for use on tubing of this weight. The pipe 7 is divided for approximately half its length by the partition 8, which should be centrally placed, this partition terminating in and being joined to a half disc, as at 9, which closes the lower end of one of the two channels into which the partition divides the tube 7. On one side of this tube and immediately' above the half disc 9 the opening 10 is formed in the wall of the tube, this opening having a projected area equal to the total area of the tube 7. The lower end of the tube 7 is closedby the disc 11, and an opening 12 is formed immediately above this disc, the area of the opening being equal to the area of the opening 10.

As it is not essential that leakage between the two channels thus formed be entirely avoided it is feasible to make the partition 8 in the form of a strip of sheet metal to which is attached, as by soldering or brazing, the half disc 9. This partition carrying the half disc may be slid into the tube 7 until the half disc comes Hush with the lower end of the openingP 10, and this strip then brazed or soldered in place inside the tube 7, at the points 30l and 31.

ile I prefer to divide the suction tube into channels as shown, the partition 8 and half disc 9 may be omitted, thus leaving the tube undivided, without materially impair- `.ing the results obtained.

The jacket 15 may be made of light sheet metal, as for instance one-sixteenth inchsteel, and the outside diameter of such jacket is preferably equal to the outside diameter of the coupling 5. The threads 25 formed inside this jacket atits upper end, and the corresponding threads on the block 6, should be the tine ,threads suited for use on thin sheet metal. A set-screw y17 may be inserted into a tapped hole passing through the wall of the jacket 15 and into the block 6, the purpose of this set-screw being to prevent the jacket from unscrewing from the block 6. The lower end of the jacket 15 may be closed in any preferred manner, as for instance by the dished head' 16, also made of light sheet metal and welded or brazed to the jacket 15. The inside ofthe jacket 15 should be reamed to an even diameter and brought t0 a smooth finish, at least so far from its upper end as the line 3 3, which should be slightly less than half its total length.

To the outside of the tube 7 should be affixed the annular ring 13, which may be of relatively light metal and made fast to the tube 7 by brazing or soldering, as in the point 14. The outside diameter of this ring should be such as to make a neat sliding fit inside the upper portion of the jacket 15 when said jacket is slid thereover in assembling the anchor. It will be noted that this device may be assembled by screwing the pipe 7 into the block 6 and thereafter sliding the jacket 15 over the tube 7 and the ring 13 and screwing it into position over the block 6, finally locking it in position by the screw 17. The anchor may be thus assembled either before or after the block 6 is i screwed into the collar 5.

In the upper half of the jacket 15 are formed two groups of perforations, represented at 20 and 21. The upper group 20 should be so situated as to lie immediately below the block 6 when the jacket is screwed into position. The 'lower group 21 should be situated at least some inches, and preferably a foot or more, below the upper group 20. These perforations may if preferred be carried entirely-around the jacket 15 in two rings or bands.

Two similar 'sets of perforations should be formed in the lower half of the jacket. The spacing of these perforations should be substantially the same as the spacing of perforations 20 and 21, and their position in regard to the annular ring 13 should be the same as the position of the perforations 20 and 21 in regard to the lower end of the block 6. It will be noted that the annular ring 13 divides the jacket 15 into two separate and independent chambers.

'The purpose of the perforations 21 and 23 is to admit oil containing some gas into the chambers 18 and 19 respectively. The total area of these perforations should be calculated in the manner set forth below, but the area of perforation is no part of my present invention and I do not limit myself to any given perforation area.

e purpose of the perforations 20 and 22 is to allow separated gas to escape from the chambers 18 and 19 respectively, and the total area of each of these groups of perforations may be materially less than the area of the groups 21 and 23, for instance the area of the gas perforations may be substantially one-half the area of the oil perforations, or even smaller.

It is well known that the rate at which bubbles of gas will rise through a mass of oil varies` with the size of the bubbles and the velocity of the oil. Inasmuch as the size of the gas bubbles liberated from but stilly entrained in the oil may be considered to vary over an indefinite range it is impossible to so retard the velocity of the oil as to permit all of the gas to escape. I have discovered, however, that if the velocity of the oil entering the perforations 21 and 23 be not greater than two inches per second, and if the velocity in the downpass of the gas anchor (as for example in traveling from the perforations 21 into the opening 10 or from the perforations 23 into the opening 12) be not more than six inches per seconds, so large a proportion of the gas will escape and separate from the oil as to permit highly eflicient operation of the anchor. The preferable area of the holes 21 and 23 and of the annular space between pipe 7 and jacket 15 may be calculated on this basis.

The construction disclosed herein is such that the greatest possible free cross sectional area may be obtained by the use of thin walled smooth tubing, which occupies the least possible space in a narrow caslng, and which sets up the least possible turbulence tending to counteract the separation of gas from oil b gravity. These features of my invention, owever, I am claiming in a separate application and in this present a plication I restrict my claims to the use ,o two or more gas anchors, laced in tandem but functioning in paralle by which construction the velocity of the oil through the downpass, for any given rate of ow into the pump suction, is divided by the number of units into which the device is divided. It will be obvious that while onl two independently acting anchors are s own in the unit construction here disclosed, it would be entirely `feasible to use three or even more in the same manner.

I claim as m invention:

1. A gas anc or comprising: a pump-suction tube divided longitudinally into a plurality of channels of unequal length, a closure at the bottom of each channel except the longest, a shield surrounding said suction tube'leaving an annular space therebetween, partition at the level of each closure for dividing said annular space into chambers equal in number to said channels, means of communication between each chamber and the corresponding channel located substantially at the lower end of each chamber, and openings through said shield located' substantially at the upper end of each chamber.

2. A gas anchor for placing in a well casing, comprising: a plurality of downass separating chambers arranged in tan em, each communicating at or near its top with the interior of the casing and communicating at or near its bottom with a pump suction tube.

In witness that I claim the foregoing I have hereunto subscribed my name this 23rd day of May, 1927.

HALLAN N. MARSH. 

